The present invention relates to laminated sheet materials that are used in the construction of various types of buildings. As is known to those familiar with such construction, sheet material is desirably used for insulation, moisture barriers, vapor barriers, and other related construction needs.
One method of providing these properties in a building is in the form of laminated structures which are made up of several types of sheets having different, selected properties. For example, by laminating a moisture barrier sheet such as a plastic or polymeric material to a metal foil, the resulting structure can serve as both an insulator and as a moisture barrier.
Such laminated sheet structures are particularly useful in certain types of buildings where the interior or exterior construction of the building may make the use of other sorts of materials uneconomical, difficult, or even impossible. For example, the increasingly popular metal buildings provide a relatively economical method of producing useful structures with ease of construction and at moderate cost. Although the metal framework, walls, and roofing of such buildings are structurally sound, they generally provide little or no thermal insulating properties, and similarly offer the opportunity for moisture or vapors to pass through the building at the joints between the various subparts. Thus, some form of vapor or moisture barrier and some form of insulation are generally required.
In particular, because moisture reduces the effective R-value of fiberglass insulation, a moisture barrier can help maintain the insulation's R-value by preventing moisture from reaching the fiberglass portion of a building's insulation structure.
Laminate sheet structures offer a useful solution to these problems. In particular, because the sheet material is flexible and thin, it is easily handled and applied to structures such as metal buildings that lack more conventional elements to provide the desired vapor and thermal properties. It will be understood, of course, that these laminates also provide similar advantages in other types of construction.
An additional property desired in most structures, including metal buildings, is that of fire resistance or suppression. There are a variety of commercially available fire retardant or suppressive chemical additives which can be incorporated in other materials and will prevent or retard the propagation of fire. It is desirable to incorporate such fire retardant or suppressant compositions into a laminate construction of the type described.
Manufacture of laminated structures is generally accomplished by joining running webs of sheet materials, usually fed from supply rolls, with an adhesive therebetween. A number of adhesives can be used, and those familiar with adhesive systems and materials such-as plastic, paper, cloth, and foil, generally select a particular adhesive from those conventionally available to join the laminate structure.
In forming a laminate, however, a sufficient amount of adhesive must be incorporated to form and maintain the laminate structure. For the type of laminates described herein, relatively high coat weights of adhesive are required; e.g. 6-10 pounds per ream. Such coat weights, however, limit the type of coating equipment that can be used. For example, differential roll coaters are generally useful for lower coat weights--around 1-3 pounds per ream--but cannot normally be used to form the laminates required for building construction.
Similarly, in order to have a useful degree of fire retardancy, the laminate must incorporate a sufficient amount of the fire retardant composition. Because the fire retardant compositions are usually solids in pigment form, they are most usefully added to the laminate structure in a liquid admixture. Thus, methods of forming such laminates must include some technique for adding the fire retardant compositions in such fashion in the desired or necessary proportions.
Additionally, where the fire retardant compositions are added to the adhesive systems, more of the overall formulated adhesive is generally required in order to obtain polymer levels that will sustain satisfactory adhesion.
Conventional adhesive systems, however, also present a problem. Specifically, they incorporate the adhesive or its precursors in some sort of solvent, usually either water or an organic solvent, depending upon the particular adhesive. The presence of the solvent, however, causes certain difficulties.
If water is the solvent, the problems generally relate to drying; i.e. time, energy, and physical space must be allotted to the drying process. All of these, of course, reduce the overall efficiency or economic favorability of such a system.
Alternatively, if an organic compound is the solvent, all of the problems that water present remains, but with the additional problem that the organic solvent may present environmental issues (e.g. release of ozone), or be toxic or otherwise hazardous, and thus must be carefully controlled prior to its release, or in some cases, prevented from any release whatsoever. Furthermore, some solvents--and thus potentially some adhesive systems--are considered hazardous enough to be presently illegal, or contemplated as being legally unavailable in the future.
Finally, although solvent free adhesives are known, they are conventionally considered to have poor "green strength" (i.e. its resistance to peeling apart as initially formed is poor, even if its cured adhesion is good) and thus unsuitable for laminate construction.
Accordingly, there exists the need for a method of producing such laminate constructions using the most advantageous equipment, incorporating the required amounts of adhesive and fire retardant composition, and while still providing the requisite vapor barrier, moisture barrier, thermal insulation, and fire retardant characteristics, but without the use of water or organic solvents.